Concurrent with the experimental demonstrations of fMRI, calculations and experiments evaluating the vascular origin of the BOLD effect were performed by our group. Calculations previously demonstrated that the BOLD phenomenon has two components, one dependent linearly and other quadratically on the main magnetic field magnitude (Bo) arising from macro-and microvasculature, respectively. Consistent with these theoretical and experimental studies, a study we performed in the last funding period demonstrated that the BOLD contrast-to-noise ratio was found to depend on magnetic field strength less than linearly in voxels containing vessels larger than the voxel itself and greater than linearly in voxels containing a mixture of capillaries and veins/venules with diameter less than that of the voxel. The experimental result in this study further demonstrates that a high magnetic field provides improved contrast for fMRI and more emphasis to more specific areas containing small vessels.